The field of invention relates to rotary spring-return operators. Flat or power springs have long been used as stand alone mechanical fail-safe devices. A spring return operator can also convert a double acting actuator to a fail safe single acting actuator when used in conjunction with, or coupled to, various types of power actuators, such as electric, pneumatic or hydraulic, to apply a torque to rotate a shaft that is coupled with, or otherwise engaged to, the shaft of the said various power actuators when desirable. For instance, spring-return actuators are commonly used as a fail-safe assembly to rotate a device, such as a valve, to a predetermined “open” or “close” position, in the event of the interruption or failure of the air, water, or electrical supply to the pneumatic, hydraulic, or electric actuators, respectively.
When used as a stand alone device a spring return operator typically returns a device such as a manually operated valve to a pre-determined safe condition. The spring return operator can be directly mounted to the device or can be adapted by means of linkage. To convert a double acting actuator to a single acting fail safe actuator take a spring-return operator coupled with a pneumatic actuator as an example, the air pressure applied to the pneumatic actuator will hold a device, typically a valve, in its normal operating position. Upon a loss of air pressure to the pneumatic actuator, the rotary spring return fail-safe operator rotates the device to a safe condition, which depending on the specific application, could be an open or a close position.
The use of a rotary spring-return operator requires a minimum amount of energy to be stored in the spring, also referred to as the spring preload, before the actuator can be operationally assembled to serve its desired purpose as an integral part of a larger assembly. The inadvertent release of the stored energy stored in the spring, such as a sudden spring pop-out during disassembly, has caused serious injuries to personnel and equipment. Therefore, for reasons of safety, it is desirable that appropriate provisions be made to prevent the inadvertent and potentially hazardous release of the stored energy within the spring of a rotary spring actuator. The preferred embodiment described below is designed in such a manner to eliminate all inadvertent and potentially hazardous release of the spring's stored tension.
Moreover, it is desirable, and at times necessary, to make adjustments to the spring-return actuators in the field, such as adjusting the spring preload, or the direction of the spring-return actuator's output rotation. In addition to the preferred embodiments' safety features described herein, the preferred embodiment also enables a user to flexibly, yet safely, make in-field adjustments to the spring rotary spring-return actuator assembly as desirable or necessary.